Q: I know getting too little sleep is bad for you, but is it possible to get too much sleep?

A: For a healthy person, it is not possible to get too much sleep. Sleep is controlled by the brain under the influence of a chemical called adenosine and the circadian rhythm. Adenosine builds up during wakefulness and causes sleepiness. The level of adenosine is reduced in the brain when a body has had enough sleep, and this will cause the person to wake up. If a person is sleeping more than normal or feeling excessively sleepy, there may be an underlying sleep disorder.